This invention relates to a guidance system using multiple sensors and more particularly to a circuit which combines the functions of a synchronous detector, amplifier and low pass filter in such a guidance system.
In guidance systems of the type which have sensors for following an externally defined path, such as magnetic coil sensors which detect an energized buried wire, the sensor signals must be detected in such a way as to eliminate spurious electronic signals referred to hereinafter as noise. Such noise can be generated by external magnetic fields as well as magnetic fields produced by the vehicle's own electro-mechanical equipment, such as electric motors and the like. A guidance system of the type which is referred to is described in U.S. Pat. No. 4,043,428.